Lubricity improver compositions and methods for improving lubricity of hydrocarbon fuels

ABSTRACT

Fuel additive compositions for enhancing the lubricity of hydrocarbon fuels in which the natural lubricity has been diminished due to treatment of the fuel to reduce sulfur and aromatic components for improved emissions are disclosed. Preferably, the fuel additive compositions include (1) a polyalkenylsuccinimide having a high molecular weight; (2) a low aromatic paraffinic base oil; and (3) a low aromatic petroleum distillate to impart improved lubricity to hydrocarbon fuels.

BACKGROUND

1. Field of the Invention

The present invention relates to additive compositions for enhancing thelubricity of hydrocarbon fuels in which the natural lubricity has beendiminished due to treatment of the fuel to reduce sulfur and aromaticcomponents for improved emissions.

2. Description of the Art

Hydrocarbon distillates and residuals used as fuel can typically containup to 5,000 ppm sulfur. The sulfur oxidizes during the combustionprocess to form SO₂ and SO₃ which, in addition to be emitted as acidgas, can also form sulfates. The sulfates then become part of the dieselengines particulate emissions. Therefore, reducing sulfur can reduceparticulate emissions. Sulfur reductions in fuel have been mandated inmany parts of the world including the U.S. and in the European Union.The result will be sulfur levels phased down to less than 15 ppm witheventual reductions to less than 5 ppm.

In many fuel systems, particularly diesel fuel systems, the fuel itselfprovides lubrication for the fuel pump and injectors. A fuel with poorlubricity can result in unacceptable wear and premature failure of theseparts. With reductions in sulfur levels, fuel lubricity is becoming abigger concern. Refining techniques and processes to reduce sulfur andaromatics in the fuel for improved emissions also reduces the naturallubricity of the fuel. This lubricity problem has been made even worseby proposed requirements to limit the maximum distillation point ofdiesel fuel.

Many refiners and fuel formulators are using lubricity improveradditives to impart acceptable lubricating properties back to the fuel.Various injector and injector pump tests and several laboratory testshave been developed to measure the lubricity of diesel fuels. ASTM D6079 High Frequency Reciprocating Rig (“HFRR”) test is the most widelyused and accepted.

The addition of minor proportions of long chain fatty acids to liquidhydrocarbon fuels to increase lubricity is well known. These types ofcompositions are described in U.S. Pat. Nos. 4,002,437 (to Broeckx, etal.) and 4,185,594 (to Perilstein). Long chain fatty acids, however, canreact with other components in many modern fuel and lubricant additivepackages resulting in loss of effectiveness and formation of undesirablegels and sludges. There is a need, therefore, for lubricity additivesthat have a reduced affinity to interact with the other fuel andlubricant additives.

Esters of long chain fatty acids have also been disclosed as fuellubricity additives. The acid group of these molecules has been blockedby the esterification reaction and, thus, is not available forinteraction with the other fuel and lubricant additives. However, thelubricity imparting function of the fatty acid has been reduced.

Amides of long chain fatty acids disclosed as fuel lubricity additiveshave the advantage of reduced affinity to react with other fuel andlubricant additives but, like the esterification reaction describedabove, amination can also result in loss or reduction of the lubricityfunction of the fatty acid. Esters and amides of fatty acids aredisclosed in U.S. Pat. Nos. 3,273,981 (to Furey) 4,204,481 (to Malec),4,729,769 (to Schlicht, et al.). Alkoxyamides are disclosed in U.S. Pat.No. 4,427,562 (to Horodysky, et al.).

Other prior compounds include reaction products of an amine, an aldehydeand mercaptan further reacted with a boron compound are described inU.S. Pat. No. 4,486,321 (to Horodysky, et. al.). However, sulfurcontaining additives are undesirable since they can increase amount ofSO_(x) emissions and are thus not consistent with efforts to reduce thesulfur content of hydrocarbon fuels.

Additionally, coupling reaction products of polyalkylene amines withheterocyclic compounds are described in U.S. Pat. Nos. 5,538,520 and5,552,069 (both to Avery, et al.). Although the resulting compounds areclaimed to provide fuel lubricity, they can contain sulfur moietieswhich can increase sulfur emissions on combustion of the fuel.

With respect to other prior compounds, U.S. Pat. No. 6,296,677 (toRibeaud, et al.) describes the reaction of various oils with activehydrogen compounds and carboxylic acids. These compounds are claimed toreduce wear in the fuel system of diesel engines operating on fuels withreduced sulfur and aromatic content. U.S. Pat. No. 6,793,696 (to Krull,et al.) discloses low sulfur diesel fuel oil compositions containingsalts of fatty acids with short chain oil soluble amines. U.S. Pat. No.6,835,217 (to DeRossa, et al.) discloses fuel compositions comprising amajor amount of hydrocarbon fuel containing at least one alcohol andsubstantially free from MTBE, and a friction modifying amount of afriction reducing agent prepared by the reaction of at least one naturalor synthetic oil with at least one alkanolamine. U.S. Pat. No. 6,872,230(to Cross, et al.) discloses reaction products of alkylated polyamineswith various ureas or isocyanates and derivatives thereof. U.S. Pat.Nos. 6,866,690 (to Aradi, et al.), 6,896,708 (to Conner, et al.) and6,923,838 (to Maubert) disclose other amides and esters of carboxylicacids and transesterification and transamidation products of natural orsynthetic oils. MacMillian, et al. in U.S. Pat. No. 6,156,082 describesa process to improve fuel lubricity and reduce corrosion by the use ofglycol esters of polyalkenylsuccinic anhydrides. None of these priorcompounds provide both significant reduction of sulfur emissions andsignificant enhancement of lubricity.

Another group of compounds used in lubricating oils arepolyalkenylsuccinimides. Polyalkenylsuccinimides are well known and areused extensively as dispersants in lubricating oils. These dispersantsfunction by surfactant action to hold polar dirt and sludge compoundsinto the oil matrix so they can be removed by filtration. Generally, thepolyalkenylsuccinimide dispersants have a relatively high molecularweight hydrocarbon tail to provide oil solubility. The molecular weightis generally in the range from about 1,000 to 2,000 daltons.

Examples of the use of polyalkenylsuccinimides as dispersants of thistype in lubricating oil compositions, and methods of preparations aredisclosed in the following U.S. Pat. Nos.; 3,873,460 (to Coon, et al.),3,897,456 (to Brewster), 4,234,435 (to Meinhardt, et al.), 4,472,588 (toKeasey), 4,713,189 (to Nalesnik, et al.), 4,857,217 (to Guiterrez),5,334,321 (to Harrison), 5,792,730 (to Guiterrez), 5,821,205 (toHarrison), 6,548,458 (to Loper), 6,770,605 (to Stachew) and 6,933,351(to Michaued), each of which is hereby incorporated by reference.

Although high molecular weight polyalkenylsuccinimides are disclosed asdispersants in oil lubricants, these compounds, to the inventor'sknowledge, are not used in fuels. The reason is thatpolyalkenylsuccinimides of the type described above, although very gooddispersants, are relatively poor detergents. As a result, when used inlubricating oils, other additives, usually containing divalent metals,are combined with the polyalkenylsuccinimides to impart detergency tothe lubricating oil. Therefore, high molecular weightpolyalkenylsuccinimides have not been desired for use in fuels becauseit is not desirable to add divalent metals to fuels.

Another class of compounds commonly known as polyalkyleneamines functionvery well as fuel detergents and are effective at cleaning intake valvedeposits (“IVD”) without contributing to combustion chamber deposits(“CCD”). Thus, polyalkyleneamines generally are utilized as fueladditives.

Although high molecular weight polyalkenylsuccinimides are not utilizedas fuel additives, low molecular weight polyalkenylsuccinimides andderivatives, i.e., having molecular weights lower than 1,000 daltons butusually 350-750 daltons are used in fuel as stabilizers because thehigher nitrogen content prevents fuel degradation during storage. Theselow molecular weight polyalkenylsuccinimides do not provide anylubricity enhancement of fuels. Accordingly, prior to the development ofthe present invention, there has been no lubricity enhancing fueladditive or process for forming lubricity enhancing fuel additives that:provide reduction in sulfur emissions; provide increased lubricity offuels, and in particular, diesel fuels; and include a high molecularweight polyalkenylsuccinimide. Therefore, the art has sought lubricityenhancing fuel additives and processes for forming lubricity enhancingfuel additives that: provide reduction in sulfur emissions; provideincreased lubricity of fuels, and in particular, diesel fuels; andinclude a high molecular weight polyalkenylsuccinimide.

SUMMARY OF THE INVENTION

A lubricity enhancing fuel additive is needed that removes one or moreof the negative characteristics associated with current fuel lubricitytechnologies. The lubricity enhancing fuel additives disclosed hereinadvantageously resist the process of readily hydrolyzing or degrading tospecies that can interact with the other additives, used in either thefuel or engine lubricant, and furthermore advantageously resistcontributing to undesirable emissions or generation of undesirableemissions and therefore should advantageously be low in sulfur and lowin aromatic content and not contain heavy metals.

Surprisingly, it has now been found that lubricity enhancing fueladditives comprising a polyalkenylsuccinimide of higher molecularweights improve the lubricity of fuels. Such polyalkenylsucinimides arenot typically used in fuel. Preferably, a low aromatic paraffinic baseoil and a low aromatic petroleum distillate are included with thepolyalkenylsuccinimide of the lubricity enhancing fuel additives toimprove lubricity of hydrocarbon fuels.

The polyalkenylsuccinimide component preferably is a mixture of amono-polyalkenylsuccinimide and a di-polyalkenylsuccinimide.

The composition of the current invention can be added to fuels of poorlubricity, such as middle distillate fuels that have been treated toreduce sulfur and aromatics including, gasoline, diesel fuel, kerosene,fuel oils and heavy fuel oils.

This new invention also comprises methods of increasing fuel lubricityby treatment of the fuel with the lubricity enhancing fuel additivesdisclosed herein.

The fuel may contain, in addition to the lubricity enhancing fueladditives disclosed herein, other additives commonly added as minorconstituents to the fuel such as cold flow improvers, antifoamadditives, cetane improvers, combustion improvers and the like. Theseother components can be added individually or as part of a completemultifunctional package.

In accordance with the disclosure herein, one or more of the foregoingadvantages can be achieved through a lubricity enhancing fuel additivecomprising a polyalkenylsuccinimide having a molecular weight greaterthan 2,000 daltons wherein the lubricity enhancing fuel additiveincreases the lubricity of a hydrocarbon fuel by at least 10 percentusing the High Frequency Rotating Rig test described in ASTM D 6079.

A further feature of the lubricity enhancing fuel additive is that thepolyalkenylsuccinimide can comprise a mono-polyalkenylsuccinimide.Another feature of the lubricity enhancing fuel additive is that thepolyalkenylsuccinimide can comprise a di-polyalkenylsuccinimide. Anadditional feature of the lubricity enhancing fuel additive is that thepolyalkenylsuccinimide can comprise a mono-polyalkenylsuccinimide and adi-polyalkenylsuccinimide. Still another feature of the lubricityenhancing fuel additive is that the mono-polyalkenylsuccinimide and thedi-polyalkenylsuccinimide can be present in a ratio of 3 to 1. A furtherfeature of the lubricity enhancing fuel additive is that themono-polyalkenylsuccinimide and the di-polyalkenylsuccinimide can bepresent in a ratio of 1 to 3. Another feature of the lubricity enhancingfuel additive is that the mono-polyalkenylsuccinimide and thedi-polyalkenylsuccinimide can be present in a ratio of 1 to 1. Anadditional feature of the lubricity enhancing fuel additive is that thelubricity enhancing fuel additive can further comprise a low aromaticparaffinic base oil having a molecular weight in the range from 250 to650 daltons and preferably in the range from 350 to 450 daltons.Further, aromatic portion of the paraffinic base oil is preferably lessthan 5% and more preferably less than 1%. Still another feature of thelubricity enhancing fuel additive is that the weight proportion of thelow aromatic paraffinic base oil can be in the range from 50 to 90weight percent of the lubricity enhancing fuel additive. A furtherfeature of the lubricity enhancing fuel additive is that the weightproportion of the low aromatic paraffinic base oil can be in the rangefrom 60 to 80 weight percent of the lubricity enhancing fuel additive.Another feature of the lubricity enhancing fuel additive is that thelubricity enhancing fuel additive can further comprise a low aromaticpetroleum distillate having a molecular weight in the range from 250 to650 daltons and preferably in the range from 350 to 450 daltons.Further, aromatic portion of the petroleum distillate is preferably lessthan 5% and more preferably less than 1%. An additional feature of thelubricity enhancing fuel additive is that the weight proportion of thelow aromatic petroleum distillate can be in the range from 5 to 50weight percent of the lubricity enhancing fuel additive. Still anotherfeature of the lubricity enhancing fuel additive is that the weightproportion of the low aromatic petroleum distillate can be in the rangefrom 15 to 40 weight percent of the lubricity enhancing fuel additive. Afurther feature of the lubricity enhancing fuel additive is that theweight proportion of the low aromatic petroleum distillate can be in therange from 20 to 25 weight percent of the lubricity enhancing fueladditive.

In another aspect, one or more of the foregoing advantages can also beachieved through a process for forming a lubricity enhancing fueladditive. The process can comprise the steps of: forming a firstpolyalkenylsuccinimide having a molecular weight greater than 2,000daltons and combining at room temperature the firstpolyalkenylsuccinimide with a low aromatic paraffinic base oil and a lowaromatic petroleum distillate to form the lubricity enhancing fueladditive, wherein the low aromatic paraffinic base oil is present in thelubricity enhancing fuel additive in a range from 50 to 90 weightpercent and the low aromatic petroleum distillate is present in thelubricity enhancing fuel additive in a range from 5 to 50 weightpercent, wherein the lubricity of the fuel is increased at least 10percent using the High Frequency Rotating Rig test described in ASTM D6079.

A further feature of the process for forming an lubricity enhancing fueladditive is that a second polyalkenylsuccinimide can be combined withthe first polyalkenylsuccinimide, the low aromatic paraffinic base oil,and the low aromatic petroleum distillate to form the lubricityenhancing fuel additive. Another feature of the process for forming anlubricity enhancing fuel additive is that the firstpolyalkenylsuccinimide and the second polyalkenylsuccinimide can becombined in a ratio of 3 to 1. An additional feature of the process forforming an lubricity enhancing fuel additive is that the firstpolyalkenylsuccinimide and the second polyalkenylsuccinimide can becombined in a ratio of 1 to 3. Still another feature of the process forforming an lubricity enhancing fuel additive is that the firstpolyalkenylsuccinimide and the second polyalkenylsuccinimide can becombined in a ratio of 1 to 1. A further feature of the process forforming an lubricity enhancing fuel additive is that the firstpolyalkenylsuccinimide can comprise a mono-polyalkenylsuccinimide andthe second polyalkenylsuccinimide can comprise adi-polyalkenylsuccinimide.

In a particularly preferred embodiment, the lubricity enhancing fueladditive contains only a polyalkenylsuccinimide, a low aromaticparaffinic base oil, and a low aromatic petroleum distillate. In stillanother preferred embodiment, the lubricity enhancing fuel additiveincludes a polyalkenylsuccinimide, a low aromatic paraffinic base oil,and a low aromatic petroleum distillate, a dispersant, a solvent, andother non-functional elements from the formation of thepolyalkenylsuccinimide. In either of the foregoing embodiments, thepolyalkenylsuccinimide can include one or both ofmono-polyalkenylsuccinimide or di-polyalkenylsuccinimide.

As mentioned above, the lubricity enhancing fuel additives and processesfor forming lubricity enhancing fuel additives have the advantages of:providing reduction in sulfur emissions; providing an increase in thelubricity of fuels, and in particular, diesel fuels; and including ahigh molecular weight polyalkenylsuccinimide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Fuels may be treated with the composition of the current invention atweight proportions of 1 to 10,000 ppm, preferably between 5 and 5,000ppm and most preferably between 800 and 1,600 ppm to impart improvedlubricity characteristics to the fuel.

The mono-polyalkenylsuccinimide can be represented by the generalstructure (I):

where R is a polyisobutenyl group and may be from 150 to 3,000 molecularweight, preferably from 500 to 1,200 molecular weight and mostpreferably from 800 to 1,200 molecular weight; y can be an integer from0 to 10 and preferably from 2-10 and most preferably from 2-5.

The di-polyalkenylsuccinimide can be represented by the generalstructure (II):

where R is a polyisobutenyl group and may be from 300 to 3,000 molecularweight, preferably from 1,200 to 2,800 molecular weight and mostpreferably from 2,200 to 2,800 molecular weight; y can be an integerfrom 0 to 10 and preferably from 2-10 and most preferably from 2-5.

The weight ratio of polyalkenylsuccinimide of structure I to structureII can range from 99:1 to 1:99, preferably from 75:25 to 25:75 and mostpreferably 50:50.

The weight proportion of the low aromatic paraffinic base oil can rangefrom 50 to 90%, preferably from 50 to 85%, and most preferably from 60to 80%.

The weight proportion of the low aromatic petroleum distillate can rangefrom 5 to 50%, preferably from 15 to 40% and most preferably from 20 to25%.

The weight proportion the polyalkenylsuccinimide of Structure I andStructure II combined can range from 1 to 10%, preferably from 2 to 8%and most preferably from 4 to 8%.

In addition to the composition specified above, the total base number(“TBN”), as measured by ASTM D 2896, is a specification and ispreferably at least 1 mg KOH/gram and most preferably greater than 3 mgKOH/gram.

The low aromatic paraffinic base oil can be an API Group II, III or IVbase oil or white oil or mixtures thereof. The aromatic content can beless than 5 ppm, preferably less than 2 ppm and most preferably lessthan 1 ppm. The paraffinic content can be greater than 80%, morepreferably greater than 85% and most preferably greater than 90%. Thesulfur content may be less than 300 ppm, preferably less than 200 ppmand most preferably less than 100 ppm.

The low aromatic light petroleum distillate may have a boiling point ofless than 300° C., preferably less 250° C. and most preferably less than225° C. and a flash point greater than 50° C., preferably greater than55° C. and most preferably greater than 60° C. The aromatic content maybe less 5 ppm, preferably less than 2 ppm and most preferably less than1 ppm. The sulfur content may be less 5 ppm, preferably less than 2 ppmand most preferably less than 1 ppm.

Preparation of Compounds Example I Mono-Polyalkenylsuccinimide (I)

A reaction mixture containing 98 grams (1.0 mole) of maleic anhydrideand 950 grams (1.0 mole) of TPC 595 (highly reactive polyisobutylene of950 molecular weight, available from Texas Petrochemicals) was heated at240° C. for 6 to 8 hours. The mixture was then vacuum stripped to removeun-reacted maleic anhydride and cooled to less than 80° C. Thisintermediate polyalkylenesuccinic anhydride (“PIBSA”) was light yellowin color, free of char with a saponification number of 118 and aresidual maleic anhydride content of less 0.1%. The PIBSA was mixed with100 milliliters of toluene. While maintaining the pot temperature at70-80° C., 146 grams (1.0 mole) of triethylenepentamine (“TEPA”) wasadded over a one-hour period and then allowed to digest for anadditional hour. The reaction mixture was heated to 110° C. and thewater of reaction was removed by azeotropic distillation with toluene.The distillation was continued until the theoretical amount of water andall of the toluene was removed. A vacuum was applied to remove anyun-reacted TEPA. The resulting polyalkenylsuccinimide (“PIBSI”) producthad a nitrogen content of 4.7% and was diluted to 2% nitrogen with 100 Nbase oil and cooled to room temperature.

Example II Di-Polyalkenylsuccinimide (II)

A lab preparation was conducted as above except 2,300 grams (1.0 moles)of TPC 5230 (highly reactive polyisobutylene of 2,300 molecular weight,available from Texas Petrochemicals) and 98 grams (1.0 mole) of maleicanhydride was reacted at 240° C. for 4 hours and the reaction continuedat 260° C. for an additional 4 hours. The PIBSA intermediate was darkyellow in color and had a saponification number of 77 and a residualmaleic anhydride content of less than 0.1%. After cooling to 70-80° C.,100 milliliters of toluene was mixed with the PIBSA and 73 grams (0.5moles) of TEPA was added over a one-hour period. The reaction mixturewas digested for an additional hour and then heated to 110° C. and thewater of reaction was removed by azeotropic distillation. Thedistillation was continued until the theoretical amount of water and allof the toluene was removed. A vacuum was applied to remove anyun-reacted TEPA. The resulting polyalkenylsuccinimide (“PIBSI”) productwhich had a nitrogen content of 2.1% was diluted to 1% nitrogen with 100N base oil and cooled to room temperature.

Example III Formulation of Fuel Lubricity Composition

A composition capable of imparting lubricity to fuels was prepared bymixing 244 grams of Motiva Star 4 base oil, 78 grams of Ashland Solvent142, 10 grams of mono-polyalkenylsuccinimide from Example I and 10 gramsof di-polyalkenylsuccinimide from Example II. The mixture was stirred atroom temperature (19-25° C.) until a clear light yellow solution with anitrogen value of 870 ppm was obtained. The TBN was 3.45.

Improvement of Fuel Lubricity

The High Frequency Rotating Rig (“HFRR”) test described in ASTM D 6079can measure the lubricity of fuels and fuels treated with lubricityadditives. The results are reported as wear on the surface of theoscillating ball measured as mean scar diameter in microns. Lower wearscar diameters are indicative of better fuel lubricity.

HFRR scar diameters are compared in Table 1 for a reference ultra-lowsulfur diesel fuel (“ULSD”) containing 8 ppm Sulfur with the same ULSDdosed with the composition of Example III.

The fuel lubricity composition of the current invention reduced the wearscar by 18%, clearly demonstrating a substantial improvement in fuellubricity.

TABLE 1 High Frequency Reciprocating RIG (“HFRR”) Test at 60° C. WithUltra-Low Sulfur Diesel Containing 8 ppm Sulfur Example III AdditiveConcentration (mg/kg) Wear Scar Diameter (microns) 0 595 800 484 1600487

It is to be understood that the invention is not limited to the exactdetails of construction, operation, exact materials, or embodimentsshown and described, as modifications and equivalents will be apparentto one skilled in the art. Accordingly, the invention is therefore to belimited only by the scope of the appended claims.

1. A lubricity enhancing fuel additive comprising apolyalkenylsuccinimide having a molecular weight greater 2,000 daltons,wherein the lubricity enhancing fuel additive increases the lubricity ofa hydrocarbon fuel by at least 10 percent using the High FrequencyRotating Rig test described in ASTM D
 6079. 2. The lubricity enhancingfuel additive of claim 1, wherein the polyalkenylsuccinimide comprises amono-polyalkenylsuccinimide.
 3. The lubricity enhancing fuel additive ofclaim 1, wherein the polyalkenylsuccinimide comprises adi-polyalkenylsuccinimide.
 4. The lubricity enhancing fuel additive ofclaim 1, wherein the polyalkenylsuccinimide comprises amono-polyalkenylsuccinimide and a di-polyalkenylsuccinimide.
 5. Thelubricity enhancing fuel additive of claim 4, wherein themono-polyalkenylsuccinimide and the di-polyalkenylsuccinimide arepresent in a ratio of 3 to
 1. 6. The lubricity enhancing fuel additiveof claim 4, wherein the mono-polyalkenylsuccinimide and thedi-polyalkenylsuccinimide are present in a ratio of 1 to
 3. 7. Thelubricity enhancing fuel additive of claim 4, wherein themono-polyalkenylsuccinimide and the di-polyalkenylsuccinimide arepresent in a ratio of 1 to
 1. 8. The lubricity enhancing fuel additiveof claim 1, further comprising a low aromatic paraffinic base oil. 9.The lubricity enhancing fuel additive of claim 8, wherein the weightproportion of the low aromatic paraffinic base oil is in the range from50 to 90 weight percent of the lubricity enhancing fuel additive. 10.The lubricity enhancing fuel additive of claim 8, wherein the weightproportion of the low aromatic paraffinic base oil is in the range from60 to 80 weight percent of the lubricity enhancing fuel additive. 11.The lubricity enhancing fuel additive of claim 8, further comprising alow aromatic petroleum distillate.
 12. The lubricity enhancing fueladditive of claim 11, wherein the weight proportion of the low aromaticpetroleum distillate is in the range from 5 to 50 weight percent of thelubricity enhancing fuel additive.
 13. The lubricity enhancing fueladditive of claim 11, wherein the weight proportion of the low aromaticpetroleum distillate is in the range from 15 to 40 weight percent of thelubricity enhancing fuel additive.
 14. The lubricity enhancing fueladditive of claim 11, wherein the weight proportion of the low aromaticpetroleum distillate is in the range from 20 to 25 weight percent of thelubricity enhancing fuel additive.
 15. A process for forming anlubricity enhancing fuel additive, the process comprising the steps of:forming a first polyalkenylsuccinimide having a molecular weight greaterthan 2,000 daltons; combining at room temperature the firstpolyalkenylsuccinimide with a low aromatic paraffinic base oil and a lowaromatic petroleum distillate to form the lubricity enhancing fueladditive, wherein the low aromatic paraffinic base oil is present in thelubricity enhancing fuel additive in a range from 50 to 90 weightpercent and the low aromatic petroleum distillate is present in thelubricity enhancing fuel additive in a range from 5 to 50 weightpercent, wherein the lubricity of the fuel is increased at least 10percent using the High Frequency Rotating Rig test described in ASTM D6079.
 16. The process of claim 15, wherein a secondpolyalkenylsuccinimide is combined with the firstpolyalkenylsuccinimide, the low aromatic paraffinic base oil, and thelow aromatic petroleum distillate to form the lubricity enhancing fueladditive.
 17. The process of claim 16, wherein the firstpolyalkenylsuccinimide and the second polyalkenylsuccinimide arecombined in a ratio of 3 to
 1. 18. The lubricity enhancing fuel additiveof claim 16, wherein the first polyalkenylsuccinimide and the secondpolyalkenylsuccinimide are combined in a ratio of 1 to
 3. 19. Thelubricity enhancing fuel additive of claim 16, wherein the firstpolyalkenylsuccinimide and the second polyalkenylsuccinimide arecombined in a ratio of 1 to
 1. 20. The lubricity enhancing fuel additiveof claim 16, wherein the first polyalkenylsuccinimide comprises amono-polyalkenylsuccinimide and the second polyalkenylsuccinimidecomprises a di-polyalkenylsuccinimide.